When people suffer from some types of heart arrhythmias, the result may be that blood flow to various parts of the body is reduced. Some arrhythmias may even result in a Sudden Cardiac Arrest (“SCA”). SCA can lead to death very quickly, e.g. within 10 minutes, unless treated in the interim.
Some people have an increased risk of SCA. People at a higher risk include individuals who have had a heart attack, or a prior SCA episode. These people receive the recommendation to receive an Implantable Cardioverter Defibrillator (“ICD”). An ICD continuously monitors the person's electrocardiogram (“ECG”). If certain types of heart arrhythmias are detected, then the ICD delivers an electric shock through the heart.
After being identified as having an increased risk of an SCA, and before receiving an ICD, these people are sometimes given a wearable cardiac defibrillator (“WCD”) system. A wearable defibrillator system typically includes a harness, vest, or other garment for wearing by the patient. The system includes a defibrillator and external electrodes, which are attached on the inside of the harness, vest, or other garment. When the person wears the system, the external electrodes may then make good electrical contact with the person's skin, and therefore can help monitor the person's ECG. If a shockable heart arrhythmia is detected, then the defibrillator delivers the appropriate electric shock through the person's body, and thus through the heart.
A challenge occurs at the electrode/skin interface. The challenge occurs if there were to be a gelled electrode, because the gel can dry out and irritate the person's skin, while undesirably increasing the impedance.